This invention involves a combustion chamber designed to burn waste materials, including hazardous chemicals.
Various types of combustion chambers have been developed to burn waste materials such as waste oil, hazardous chemicals, and garbage. One of the primary reasons for burning waste material is simply to dispose of it; however, the burning of waste may also serve as a source of usable heat (for example, it can be used to heat buildings or to generate steam in a manufacturing or chemical processing facility). As used herein, the term "burning" is interchangeable with "combustion."
It is widely known that complete combustion, which reduces air pollutants and increases energy output, can be promoted by increasing the mixing of the burning material with an oxygen-containing gas such as air or purified oxygen. Along those lines, various devices and components have been incorporated into combustion chambers to increase the air-fuel mixing inside those chambers.
For example, the combustion chamber shown in U.S. Pat. No. 2,072,731 (Crosby, 1937) contains two burning zones, which can be regarded as a primary burning zone and a secondary burning zone. Fresh air is slightly compressed by a fan near one end of the chamber. Part of the air enters a central burning chamber through a first set of inlets. The central burning chamber contains a spray nozzle near the inlet, which injects the fuel into the chamber in small droplets. The fuel is ignited by a spark plug and burns, thereby creating a primary burning zone near the spray nozzle. The remaining portion of the fresh air enters an annulus which surrounds the central chamber. The air passing through the annulus is heated by the high temperatures in the central burning chamber. After being heated, the air enters the central chamber through orifices near the outlet of the device, which pass through the wall that separates the central chamber from the annulus. A secondary burning zone is created when the heated air enters the central chamber and mixes with the partially burned fuel.
Another combustion device is described in U.S. Pat. No. 2,059,523 (Hepburn et al, 1936). In that device, outside air is drawn into a secondary burning zone by means of a draft-producing device at the end of the combustion tube.
U.S. Pat. No. 4,054,028 (Kawaguchi, 1977) describes a combustion device similar to the device of Crosby, except that the air which enters the annulus does not enter the internal burning chamber through numerous small orifices. Instead, it enters the chamber through a small number of "scoops" placed in two distinct stages. Fresh air enters through a primary inlet which surrounds a fuel spray nozzle. The primary burning zone is immediately downstream from the spray nozzle. The secondary burning zone is created by a first set of scoops, which convey heated air from the annulus into the central burning chamber. A second set of scoops also serve as passageways for fresh air; however, those scoops do not create a tertiary burning zone. Instead, they create a dilution zone which assertedly controls the temperatures generated in the combustion chamber, and which presumably reduces the temperatures of the exhaust gases.
The Kawaguchi system can also contain various devices to promote air-fuel mixing, such as (1) angled blades in the primary air inlet, to generate a swirling action in the primary burning zone; (2) baffle disks between the primary and secondary burning zones, to generate turbulence and mixing; and (3) air scoops which are slanted in the upstream direction to generate turbulence and mixing in the secondary burning zone.
U.S. Pat. No. 4,173,118 (also by Kawaguchi, 1979) discloses a similar device with (1) numerous fuel spray nozzles and air inlets, spaced in a circle to create a primary burning zone with an annular rather than circular shape; (2) a water or steam injector in the middle of the primary burning zone, to aid the burning of heavy oil. That system also contains a secondary burning zone, and a dilution and cooling zone, similar to U.S. Pat. No. 4,054,028.
U.S. Pat. No. 2,398,654 (Lubbock et al, 1946) and U.S. Pat. No. 4,819,438 (Schultz 1989) also describe a combustion chambers with primary and secondary burning zones followed by a dilution zone. In the Lubbock patent, the air in the annulus flows in a direction counter to the flow of the exhaust gas, which causes it to be heated before it enters the primary burning zone. In the Schultz patent, steam is circulated around the burning chamber to control the temperature and to obtain a useful work output.
U.S. Pat. No. 3,567,399 (Altmann et al, 1971) discloses an afterburner. Hot waste gases from a primary burning chamber are introduced along with an additional source of fuel such as natural gas which is ignited near the inlet. Air is compressed into an annulus surrounding the afterburner chamber, and enters the afterburner through various orifices which are preferably angled to promote a swirling motion inside the afterburner.
The combustion chambers described above which are designed for burning waste material suffer from various limitations. The more complex devices, such as the burning chambers invented by Kawaguchi, must be assembled from dozens of component parts, which must be manufactured with close tolerances at relatively high expense. In addition, a complex burning devices can be difficult to maintain properly, especially if used to burn waste material having a wide variety of characteristics. The simpler devices such as the burners invented by Crosby, Lubbock, and Schultz do not ensure the desired degree of combustion in some situations, and can cause the emission of smoke, unburned hydrocarbons, and other air pollutants. In addition, none of the devices above are suitable for burning solid wastes.
Other devices have been developed to promote air-fuel mixing in gas turbines and jet engines; for examples, see U.S. Pat. No. 3,593,518 (Gerrard, 1971), U.S. Pat. No. 3,937,007 (Kappler, 1976), and U.S. Pat. No. 2,930,194 (Perkins, 1960). Those are not relevant to the subject invention, for several reasons. Gas turbines and jet engines involve extremely high gas velocities, the internal mechanisms involve rapidly-moving and often delicate components, they are usually operated at very high levels of excess oxygen, and they cost a great deal more to manufacture than waste oil burners.
There is, therefore, a need for a sturdy and inexpensive device for burning waste material, which has no internal moving parts and which can achieve higher levels of combustion of burnable material than previously achieved by other combustion chambers.
One object of this invention is to provide a simple, sturdy, inexpensive, and reliable device for burning waste material.
Another object of this invention is to provide a waste-burning device which can achieve virtually complete combustion of any liquid or liquified input material, such as waste oil, paint sludge, or hazardous chemicals.
Another object of this invention is to provide a device for achieving virtually complete combustion of hazardous chemical wastes, to ensure that very low quantities of toxic, carcinogenic, or otherwise hazardous air pollutants will be emitted into the atmosphere.
Another object of this invention is to provide a device for achieving virtually complete combustion of solid wastes such as old tires and municipal or industrial trash or garbage.